1. Field of the Invention
The present invention relates to a depth estimation data generating device, a computer-readable recording medium having a depth estimation data generating program recorded thereon, and a pseudo-stereo image display device, and particularly to a depth estimation data generating device, a computer-readable recording medium having a depth estimation data generating program recorded thereon, and a pseudo-stereo image display device for generating pseudo-stereo images from normal still images or videos i.e., images which are not provided with depth information (non-stereo images) explicitly or even implicitly, as with stereo images.
2. Description of the Related Art
In order to enable viewing of non-stereo images by pseudo-stereo viewing, a stereo display system performs a process of generating pseudo-stereo images from normal still images or videos i.e., images which are not provided with depth information (non-stereo images) explicitly or even implicitly, as with stereo images.
As such a technical example, there is conventionally known a perspective-based approach such as a technique disclosed, for example, in patent document 1 (Japanese Patent Application Laid-Open Publication No. H09-185712) which presumes construction of a tube with contours as its cross sections in accordance with the depth.
The technique disclosed in patent document 1 adds distance information of contours to mesh image data to form 3-dimensional polygon solid data, and applies color image data obtained from photograph images to the 3-dimensional polygon solid data. Subsequently, the 3-dimensional polygon solid is rendered in a manner attaching color image data inside the 3-dimensional polygon solid constructed by the 3-dimensional polygon solid data so that 3-dimensional image data is obtained.
In addition, there is technique disclosed in patent document 2 (Japanese Patent Application Laid-Open Publication No. 2006-185033) as another conventional example. In order to determine a scene structure as close to reality as possible, the pseudo-stereo image generating device disclosed in patent document 2 determines synthesis ratio according to a high-pass component evaluation value from an upper high-pass component evaluation unit and a lower high-pass component evaluation unit using a plurality of basic depth models indicating depth values for each of a plurality of scene structures to be the basis, and synthesizes a plurality of basic depth models in accordance with the synthesis ratio. An adder then superimposes the synthesized basic depth model and R signals of a non-stereo image, generates the final depth estimation data, and performs a process on the basis of the depth estimation data on video signals of the non-stereo image to generate video signals of a different-viewpoint image which provides a stereoscopic effect.
However, the technique disclosed in patent document 1 is based on perspective and thus has a problem of limited effects because perspective structure estimation in practice does not necessarily fit all the scenes of various non-stereo images to be input. In addition, even if perspective structure estimation is suited, there has also been a problem that it is not easy to realize stereoscopic vision without a sense of strangeness by automatically constructing a correct depth structure model.
Furthermore, the technique disclosed in patent document 2 generates depth estimation data by synthesizing a plurality of basic depth models and superimposing R signals with the synthesized basic depth model. However, if the R signals to be superimposed are concentrated near a large value in a screen, the expected pseudo-stereo effect is not sufficient because only a part of the dynamic range available as the depth estimation data is being used.
For example, referring to FIG. 1, since the R signals are reduced to 1/10 and superimposed in patent document 2, input of the R signals is reduced to 1/10 in FIG. 1. Denoting the average, the maximum value, and the minimum value of the R signals as APL, MAX, and MIN, respectively, the range actually used by the R signals becomes significantly narrower than the dynamic range, as shown in an enlarged view illustrated at the lower part of FIG. 1. Therefore, only a part of the dynamic range is used, and thus a sufficient pseudo-stereo effect can not be obtained.